> It's significantly faster than most other dynamic languages. It's fast as a compilation target to the extent we can run Unreal Engine in the browser. So I consider the original comment I replied to that simply stated 'Bad performance' incorrect or at least lazy/contextless criticism.

The entire point of my comment is that the statement "JavaScript is faster than other dynamic languages" is lazy/contextless praise.

V8 is fast. Rhino is slow. JScript 5 is really slow. They are all JavaScript. V8 is fast because people really wanted it to be fast and did some impressive cutting-edge work to make it happen, not because the language lends itself well to speed. It is a credit to the skill of the people working on the JavaScript engines that JavaScript programmers nowadays can enjoy decent speed, and AFAIK it's not particularly attributable to any specific features of the language.